The present invention relates to a tow bar assembly adapted to allow a tractor vehicle to tow a trailer vehicle and is particularly adapted for use in towing a four-wheel drive vehicle by another vehicle. The tow bar assembly includes a mounting member which is adapted to be attached either directly or indirectly to the frame of one of the vehicles and a tow bar member which is releasably securable to the mounting member at one end and which has a standard ball-type hitch at its opposite end. In the past, various towing structures have been provided between vehicles, and it is quite common for such structures to be attached to the frame of one of the vehicles with the vehicles being releasably connected by means of some sort of towing bar. Thus, this basic structure is fairly well understood and developed in the prior art, although the present invention embodies improvements over this basic structure.
An example of a known tow assembly structure is disclosed in U.S. Pat. No. 3,891,237, issued to Allen, wherein an elongated mounting member is provided with a bell-shaped socket which lockably receives the tongue of a trailer ball hitch member. The mounting member is adapted to be attached to the trailer vehicle with the trailer ball hitch member matably receiving a tow ball connected to the tractor vehicle. Similarly, U.S. Pat. No. 2,693,368 to Petron discloses a tow bar consisting of an elongated member which adjustably telescopes within a sleeve and is latched by a spring pall in a selected position. This tow bar interconnects coupling elements attached to the frame of the tractor and trailer vehicles. Another patent which discloses the general arrangement described above is U.S. Pat. No. 3,768,837 issued to Reese, wherein an enlarged frame member is attachable to the underside of the vehicle with this frame member supporting a square tube socket which releasably receives a shank member of a ball hitch.
While these inventions have allowed the towing of one vehicle by another, it has been found that, in many circumstances, it is desirable to limit the degrees of freedom about which the various connecting elements of a tow bar assembly may pivot. In the case of the connection of a tow bar to the tractor vehicle, it has been found suitable to allow either two or three degrees of freedom for rotation about the connecting element while at the trailer vehicle, it has been found desirable to limit the degrees of freedom to a single axis of rotation. By so limiting the rotation about the connecting element at the trailer vehicle, the frequency of certain undesirable tendencies, such as jack-knifing or fishtailing can be diminished.
It is also desirable that a tow bar assembly be quickly and easily attachable between a tractor vehicle and a trailer vehicle. Further, should any portion of the assembly be permanently attached to one or the other of the vehicles, the same should be as unobtrusive as possible yet readily accessible. Some existing tow bar assemblies, such as are often used with four-wheel drive vehicles, comprise an A-shaped frame where the ends of the legs are pivotally connected to the bumper of the four-wheel drive vehicle. When not in use, this assembly is positioned in a verticle orientation, but, when the user desires to tow the vehicle, the assembly is pivoted to a generally horizontal orientation for connection to a tractor vehicle. While this assembly is suitable in terms of strength for the towing operation, it has the disadvantage of being permanently affixed to the four-wheel drive vehicle and often obscures a portion of the driver's vision when it is placed in the vertical storage position.
From the foregoing, it may be appreciated that there is a need for a structurally strong tow hitch assembly which is quickly and easily interconnected and removed from a tractor and trailer vehicle. Further, it should be appreciated that where a portion of the tow hitch assembly remains attached to one of the tractor or trailer vehicles, that permanent element should be as unobtrusive as possible in order to avoid blocking a driver's vision and to avoid unwanted projections which could injure anyone moving around the vehicle.